Organometallic Elaboration as a Strategy for Tuning the Supramolecular Characteristics of Aza-Crown Ethers

Outfitting an aza-crown ether with an organotransition-metal pendant provides a mechanism for tuning its supramolecular properties. The binding affinity can be tuned by more than 2 orders of magnitude by changing the identity of the transition metal-center, altering the overall charge of the complex, or engaging in organometallic ligand substitution reactions. High Li+ selectivity (up to 29-fold higher affinity in comparison to Na+), proton-responsive behavior, and ion pair (ditopic) binding capabilities are observed in the metalla-crown ethers.